Ooh let me, let me There's a search feature - there are tons of threads about the PV muffler

I don't know why it's so popular, but it is. It's sold here, the mfr's page on it is here, and they claim "at least 15 Rear Wheel Horsepower" which is quite an improvement for a muffler in my experience. The owner of this site did a small review on the muffler here.